In general, the machines of this type known to date comprise at least one longitudinal channel for the input of one log and at least one output channel of rolls resulting from the cutting of such log.
Said channels, which define a circular housing provided with the diameter corresponding to the log and to the rolls to be processed, are arranged in a succession among them and separated by a cutting device, for example a vertical blade.
In such machines, therefore, the log is made to advance between the two channels arranged in a succession and at the passage between such channels it is cut into rolls of predetermined length.
During the cutting operations it is necessary to keep the log stably constrained to the machine in order to prevent cutting errors and consequent sizing errors of the finished rolls.
To this end, the housings defined by the channels are usually sized expressly according to the diameter of the logs to be cut.
However, such embodiments exhibit the big drawback of allowing the cut of logs having the same size only.
In such machines, in fact, as the log sizes change it is necessary to stop the machine and proceed to the manual replacement of the channels with other ones having an adequate size for the new logs fed.
WO02/49814 describes an apparatus for cutting paper logs in a plurality of rolls according to the preamble of claim 1. In particular, WO02/49814 provides for circular housings for receiving the logs which comprise mobile walls for selectively varying the diameter of the same housings between a maximum diameter and a minimum diameter.
Each wall comprises an upper mobile portion and a lower mobile portion.
The lower mobile portion is connected through pins with a supporting structure on one side and with an intermediate portion of the upper mobile portion on another side.
The upper mobile portion comprises a free upper end and a base end rotatably connected to a cam.
Such cam consists of a mobile cursor in a slot inclined between a first position that corresponds to the maximum diameter of the circular housings and a second position that corresponds to the minimum diameter of the circular housings.
The movement and clamping of the housings about the logs is controlled by a particular type of actuator which acts above the housings on the free ends of the mobile walls.
As can be seen in FIG. 1 of WO02/49814, in fact, a sort of cover element is provided arranged above the housings, vertically mobile and provided with wedge elements that during the down stroke clamp the mobile walls against the logs. Such embodiment exhibits some drawbacks, among which that of deforming the logs.
In fact, such machine for exerting a predetermined side containment force on the housing walls also generates a corresponding vertical compression force on the log.
Contrary to the side containment force, the vertical compression force is not cushioned by any spring element and is directly relieved onto the frame which, being non-deformable, transfers it to the log by reaction, causing the deformation thereof. Moreover, the presence of a cover as described in WO02, that is, of the type pressed against the housings, exhibits the further drawback of interfering with the advance of the logs that could in fact bang against the same cover.
The object of the present invention is to provide an apparatus for cutting paper logs in a plurality of rolls alternative to the known embodiments of the type described in WO02/49814 and capable of solving the drawbacks of the prior art mentioned above in a very simple, inexpensive and particularly functional manner.
Another object is to provide an apparatus for cutting paper logs in a plurality of rolls capable of processing logs of various sizes without requiring the stop of the apparatus and the manual intervention of an operator and without the risk of deforming the log.
These objects according to the present invention are achieved by making an apparatus for cutting paper logs in a plurality of rolls according to claim 1. Further features of the invention are described in the dependent claims.